A solar module is known from DE 4039945 C2 . Here a number of tandem mounted, series-connected solar cells and a number of likewise tandem mounted, series-connected diodes parallel and adjacent thereto are applied to a common substrate. The diodes, like the solar cells, consist of a front and a back electrode layer and an intermediate photovoltaically active layer sequence. The series connection of the solar cells, on the one hand, and the diodes, on the other, is effected in the known solar module in the usual way by directly electrically contacting the front electrode layer of a solar cell or diode with the back electrode layer of the directly adjacent solar cell or diode. This is done by laterally leading through the particular electrode layers beyond the area of the intermediate photovoltaically active layer sequence. The series-connected solar cells, on the one hand, and the series-connected diodes, on the other, are separated from each other by a continuous groove, except for common front electrode layers of the two outermost solar cells and diodes. The totality of series-connected solar cells is thus connected in parallel with the totality of series-connected diodes.
However, the known solar module cannot optimally handle a frequently occurring problem, namely the risk of damage caused by partial shadowing of the solar module. If even one solar cell is shadowed, which can easily happen through the shadow cast e.g. by a frame when solar radiation falls obliquely on the edge of the module, the generated photocurrent of the solar module is limited by the much smaller photocurrent of the one shadowed solar cell. Simultaneously, a high voltage applied in the reverse direction forms on the shadowed solar cell, which can lead to an electric breakdown of this solar cell and irreversible damage thereto.
In order to prevent this phenomenon in optimal fashion, a diode must be connected in the reverse direction to each individual solar cell. This is not the case in the known solar module because it has a series connection of diodes in parallel with the series-connected solar cells, and not even in the reverse direction.
It is known in the art to tackle the shadowing problem by assigning to the individual solar cells diodes connected in the reverse direction. The corresponding version depicted in FIG. 5 of DE 3517414 A1 involves separate solar cells which are connected in series with each other by external wiring. Each of these solar cells has its own diode assigned thereto which is located on the same single substrate as this solar cell and also has substantially the same layer structure, but which belongs electrically to the adjacent solar cell and is connected in the reverse direction thereto via an external wiring. The total structure of this known version is evidently elaborate, however, since each individual solar cell is structurally integrated with one diode but no total module produced in integrated thin-film technology is involved.
The further known version depicted in FIGS. 1 and 2 of JP 63-228766 A involves series-connected thin-film p-i-n type solar cells of amorphous silicon to which diodes are assigned connected in parallel and in series. Solar cells and diodes are arranged one on the other, the diodes having the function of preventing a power loss possibly occurring through elevated series resistance of the cell when shadowed. The diodes are realized by a second production process with a reverse deposition sequence (n-i-p) over the actual solar cell. This method additionally requires metalization and several structuring steps after the two separate depositions for the solar cell and the diode in each case. The total structure of this version is evidently complicated and obviously difficult to control in terms of process technology.